Chapter 6 FBD Block Diagram Programming 183
MU (Modbus) function block
There is a maximum of 250 MU (Modbus) function blocks under FBD mode, can be set mode 1~5 and the function is
same as Ladder mode.
Remote IO and IO Link are precedence than MU. MU is executed when the system setting is N (No Remote IO) and
ID isn’t 0.
Function mode corresponding communication function code:
mode Communication function code
1 03 (read registers)
2 06 (write single register)
3 10 (write multiple registers)
4 01 (read coils)
5 05 (write single coil)
※ The max data length for Mode 1 and 3 is 25words. The max data length for Mode 4 is 400bits.
The coil used in MU function:
M3D: Received M3D is set to ON after received, then check-up for error. Transferring data to
target address if there is no error.
M3E: Error flag communication error flag
M3F: Time out flag M3F is set to 1 when the time from after sending to start receiving is longer
than setting, and M3D also be set to 1. M3F is automatically reset if M3D reset.
The time out time is depending communication baud rate as shown in the table below:
Baud rate (bps) Time out (ms)
4800、9600、19200、38400
125
57600 100
115200 80
※ More information about communication to see: Chapter 7 20 Points RS485 type Models Instruction.
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